The present invention relates to systems for controlling the ignition timing of internal combustion engines and more particularly to an ignition timing control system which employs a knock sensor to detect the occurrence of knocking in an engine and thereby to control the ignition timing of the engine properly.
In recent years, a variety of knock sensors and ignition timing control systems employing such knock sensor have been proposed (e.g., U.S. Pat. No. 4,002,155) and even with these sensors and control systems it has been difficult to accurately detect the occurrence of knock and properly control the ignition timing of an engine throughout the range of the engine load conditions. For instance, in the case of a known ignition timing control system in which the occurrence of knocking is detected in accordance with the vibration level from a knock sensor mounted on the engine body, the sensor's vibration level itself varies with the operating condition of the engine and thus in accordance with the decision made only on the basis of the vibration level from the knock sensor it is difficult to properly detect the occurrence of knock in each of the cylinders under all the load conditions of the engine.